ECONOMIC EVALUATION OF FUNGICIDE APPLICATION ON TARO (Colocasia

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1 , May ; Volume 2(2S) ISSN No ECONOMIC EVALUATION OF FUNGICIDE APPLICATION ON TARO (Colocasia esculenta) LEAF BLIGHT Tarla D N 1,*, Fon D E 2, Takumbo E N 1 and Fontem D A 1,3 1 Departement of Plant Protection, FASA, University of Dschang, 2 Department of Agricultural Economics, FASA, University of Dschang 3 Delaware State University, Delaware, USA. Received April 26, 2014; Revision May 05, 2014, Accepted May 26, 2014 Available Online May 31, KEYWORDS Taro Taro leaf blight Phytophthora colocasiae Fungicide spray frequency Disease severity ABSTRACT Taro is an important crop in Cameroon but yields of the crop has severely affected by pests and diseases especially leaf blight. An economic evaluation of fungicide applications on taro blight was conducted in Dschang, Cameroon, during the 2012 cropping season. A split-plot design was used, with two factors; fungicide and cultivar, replicated three times. Whole plots were assigned to five fungicide spray schedules (7, 14, 21,, and non-treated) while sub-plots were assigned to two taro cultivars; the dark green petioles ( Ibo coco ) cultivar and the light green petioles small leaves ( Ehkoueh lah ) cultivar. A fungicide, Plantomil 72 WP was applied at 3.33 kgha -1. Blight severity was scored weekly in every sub-plot, and yields were obtained at harvest. Data was subjected to the analysis of variance. Standardized area under disease progress curve (SAUDPC) was high (p = 0.005) in control plots compared to sprayed plots of the cultivars. The high SAUDPC values were correlated with low yields (16.11 t/ha) in control plots of Ibo coco compared to high yields (60.44 to t/ha) in sprayed plots. For Ehkoueh lah, yield differences between control and sprayed plots were not high, tha -1 in the control compared to to tha -1 in sprayed plots. The highest yield increase of and % for Ibo coco and Ehkoueh lah, respectively was obtained from sprayed plots. Economic analysis revealed that a fungicide spray frequency had the highest rate of return, and 6.63 and net benefits of 8.26 and 4.76 million FCFAha -1 for Ibo coco and Ehkoueh lah, respectively. Thus, taro leaf blight can be managed with monthly applications of fungicide. * Corresponding author tarladn@yahoo.fr (Tarla D N) Peer review under responsibility of Journal of Experimental Biology and Agricultural Sciences. Production and Hosting by Horizon Publisher ( All rights reserved.

2 287 Tarla et al 1 Introduction Taro (Colocasia esculenta (L.) Schott) is an important staple or subsistence crop appreciated by millions of people from developing countries (Mishra et al., 2008). It is consumed as a staple crop in West Africa, particularly in Ghana (Joshua, 2010), Nigeria (Bandyopadhyay et al., 2011) and Cameroon (Fontem & Mbong, 2011). All parts of the plant including corm, cormels, rhizome, stalk, leaves and flowers are edible and contain abundant starch (Bose et al., 2003). It is the fourteenth most consumed vegetable worldwide (Rao et al., 2010). In 2012, the total world s production was estimated at 10 million tonnes. Cameroon was the fourth taro producer in the world, and the third highest taro producer in Africa. It contributed 1.6 million tonnes to Africa s production of 7 million tonnes. Taro is cultivated in all regions of Cameroon (FAO, 2014). Taro leaf blight, caused by Phytophthora colocasiae Raciborski is the most destructive disease responsible for heavy yield losses (25 to 50 %) of taro in many countries (Gadre & Joshi, 2003). In addition, this pathogen can also causes a serious post-harvest decay of taro corms (Misra, 1997). The disease is the major constraint to taro production and is capable of compelling farmers to abandon their crop fields or rotate to other staple crops (Jackson, 1996). In Africa, taro leaf blight was first reported in Ethiopia and Equatorial Guinea in It arrived in Nigeria in 2009 (Bandyopadhyay et al., 2011) and in Cameroon in 2010 (Fontem & Mbong, 2011). In Cameroon, the disease caused many farmers to abandon their fields. Relying on the removal of all leaves with lesions as a method of control would quickly lead to a complete defoliation of the crop with consequent effects on yield (Adams, 1999). Desirable cultural characteristics and quality are often lost during breeding to produce resistant cultivars; meanwhile the choice of taro cultivars by farmers is driven by their personal tastes and market considerations (Brooks, 2005; Nelson et al, 2011). With the above weaknesses, the cultural method and the use of resistance varieties cannot control the disease satisfactorily to provide enough tubers needed by the fast growing population. Thus, an integrated disease management strategy, which seeks to protect the environment, may be of importance. Among these methods, the rational use of fungicides to control diseases is the fastest management method. This study was carried out to assess technical and economic evaluation of fungicide applications on taro blight. 2 Materials and methods 2.1 Cultural procedure Field experiments were conducted during 2012 cropping season in Dschang (5 26 N, E, and 1400 m altitude), Cameroon. Preceding crops in the site were taro (Colocasia esculenta), beans (Phaseolus vulgaris) and maize (Zea mays). Weed species in and around the site were Ageratum houstonianum, Bidens pilosa, Setaria spp., Brachiaria spp. A randomized Split-plot design was used with two factors (fungicide and cultivar) replicated three times. Fungicide regime was assigned to main plots while cultivars occupied sub-plots. Main plot measuring 4 * 2.5 m, were separated by a taro-free zone 1m wide to limit inter plot interference. Two morphologically distinct taro cultivars i.e. Ibo coco (Dark green petioles cultivar) and Ehkoueh lah (light green petioles small leaves cultivar) which were grown in the Western highlands of Cameroon used in study. The soil was ploughed to a depth of 30 cm and taro seeds were planted on the March 20, at the spacing of 1 * 0.5 m (20000 plants ha -1 ). Poultry manure was applied a day before planting, at the rate of 10t ha -1 while the second poultry manure application (6 t ha - 1 ) was conducted three months after planting. The manure was spread round the plant but 5 cm away from the stem. Mineral fertilizer (NPK 12:11: MgO+8 S) was applied at the rate of 800 kg ha -1 3 months after planting. The field was weeded both manually and chemically. Shielded sprays of paraquat (2.5 l ha -1 ) coupled with hand weeding was used to control weeds before canopy formation. Subsequent weeding was manual and carried out when necessary. Moulding was implemented after mineral fertilizer application. Corms were harvested on the November 4 and December 4, 2012 (7.5 and 8.5 months after planting) for Ibo coco and Ehkoueh lah, respectively, when most of the leaves had senesced. The corms were separated from the petioles, counted and marketable tubers weighed for each sub-plot. Marketable tuber yields were expressed as tonnes fresh weight per hectare. Yield increases attributed to fungicide protection were calculated as follows: 2.2 Fungicide application Fungicide applications were initiated the very day the first symptoms of taro blight were observed. This was on July 8, 2012, 110 days after planting (DAP). Plantomil 72 WP was applied at the rate of 3.33kg/ha (50 g in 15 L for 150 m -2 ) using a Jacto knapsack sprayer that delivers 1000 L ha -1 at a maximum pressure of 4 kg cm -2. The nozzle was the hollow cone type. In order to make the fungicide stick to the leaves, an adhesive, Polyfix (aqueous solution of polyvinyl alcohol) was added to the spray mixture at the rate of 1.33 L ha -1 (20 ml 15L m -2 ). Plots were sprayed on a 7, 14, 21 and schedule, while control plots were left non-treated. A protective screen was placed between sprayed and non-treated plots to control fungicide drift. 2.3 Disease evaluation The crop was exposed to naturally-occurring inocula in the field. Disease severity (percent leaf area diseased) was scored

3 Economic evaluation of fungicide application on taro (Colocasia esculenta) leaf blight. 288 weekly on three central row plants of each sub-plot with the aid of a 1-9 rating scale, developed by the Potato International Centre (CIP). Seventeen and twenty-one weekly ratings, initiated from the first foliar taro blight symptoms were scored for Ibo coco and Ehkoueh lah, respectively per sub-plot. Values for standardised area under diseased-progress curves (SAUDPC) were calculated from the severity data according to the formula suggested by Campbell and Madden (1990). Total returns were the values of the marketable yields obtained in each treatment. A net return for each spray frequency was calculated by deducting the cost of fungicide protection from the total return of that spray frequency. The net increase in revenue due to fungicides treatment was assessed by deducting the net return from the non-treated plot from that obtained in each fungicide spray frequency, The rate of return (net benefit/cost of fungicide protection ratio) was calculated, to determine the most economically efficient fungicide spray frequency. Where; y i = disease severity, t i= time in days and t n-t 1= duration of the epidemic in days 2.4 Economic assessment of fungicide applications Economic analyses were conducted for costs and returns to each fungicide spray frequency on each cultivar. The market price for a bucket (15 kg) of Ibo coco was 3000 FCFA (200FCFA kg -1 ) and 6000 FCFA (400 FCFA kg -1 ) for Ehkoueh lah, obtained from interviewing at random 50 taro producers and 50 local vendors. This price was used to estimate the total returns. Increase in taro yield over nontreated plots was assumed to be solely due to fungicide applications. The cost of protecting one hectare of taro with fungicide (CP) was calculated as follows: CP = ((RF X CF) + CL) n Where RF = rate of fungicide applied (3.33 kg.ha -1 ), CF = cost of a kg of fungicide (16,000 FCFA), CL = cost of labour used in protecting a hectare of taro, cost of adhesive and depreciation of the sprayer (66,000 FCFA) and n =number of fungicide applications. 2.5 Data analysis Disease progress curves for taro blight evolution were constructed for each fungicide sprayed frequency. Standardized areas under diseased-progress curves (SAUDPC) and yields for each fungicide spray frequency were subjected to the analysis of variance (ANOVA) using GENSTAT. Means were separated using Fischer s least significance difference at P= Results 3.1 Effect of variety on the severity of taro blight Taro blight severity increased rapidly immediately after the appearance of the first symptoms. The rate of increase was higher on Ibo coco as compared to Ehkoueh lah (Figure 1). The rate of increase of taro blight severity started decreasing from day 152 after planting (42 days after the first symptoms). The final disease on Ibo coco and Ehkoueh lah was 0.94 and 0.76 respectively. The SAUDPC on Ibo coco (0.75) was higher than that of Ehkoueh lah (0.63), thus, taro blight severity was higher on Ibo coco than on Ehkoueh lah. An analysis of variance showered a significant difference (p< 0.001) in the SAUDPC on the control plots of the cultivars. «Ibo coco» «Ehkoueh lah» Figure 1 Progression of taro leaf blight in two taro cultivars ( Ibo coco and Ehkoueh'lah ) not treated with Plantomil 72 WP

4 289 Tarla et al Figure 2 Progression of taro blight on Ibo coco (a) and Ehkoueh lah (b) subjected to five fungicide spray regimes. Table 1Effect of Plantomil 72 WP spray frequency on the standardized area under diseases progress curve (SAUDPC) of taro blight. Cultivar Spray schedule SAUDPC Ibo coco 0.11b 0.12b 0.16b 0.19b 0.75a Ehkoueh lah 0.16b 0.18b 0.19b 0.19b 0.63a Means of each variety with the same letter have no significant difference (p<0.05) according to Fisher s LSD. Table 2 Effect of fungicide and variety on the yield, number of tubers/ha and mean tuber weight of Ibo coco and Ehkoueh lah cultivars of taro. Variety Spray schedule Yield (t/ha) Number of tubers x1000/ha Ibo coco 16.11a 140a 62.11b 373b 61.22b 377b 60.78b 366b Mean tuber weight a b b b 60.44b 377b b Ehkoueh lah 33.11a 49.06b 48.44b 46.78b 407 a 436 a 441 a 427 a 81.90a b b b 46.83b 417 a b Means of each variety in the same column with the same letter are not significantly different (p<0.05) according to Fisher`s LSD.

5 Economic evaluation of fungicide application on taro (Colocasia esculenta) leaf blight. 290 Table 3 Percent yield increases of Ibo coco and Ehkoueh lah attributed to applications of Plantomil 72 WP. Spray schedule Yield increase (%) due to fungicide sprays Ibo coco Ehkoueh lah Table 4 economic analysis (million FCFA/ha) of Plantomil 72 WP spray schedule to manage taro blight. Cultivar Spray frequency Total return from sprayed plots(a) Total return from nontreated plots (b) Net return (c= a-b) Cost of fungicide and application (d) Net benefit e=c-d Rate of return (f=e/d) Ibo coco Ehkoueh lah Effect of fungicide spray frequency on taro blight severity Taro blight severity on both cultivars was lower in sprayed plots than control plots. (Figure 2) The final disease was below 25 % for sprayed plots contrary to non-treated plots, which had 94 and 77 % for Ibo coco and Ehkoueh lah, respectively. An analysis of variance revealed a highly significance (p < 0.001) effect of spay frequency on SAUDPC. plots were significantly different from sprayed plots at P < There existed no significant different (p< 0.05) between sprayed plots of each cultivar (Table 1). 3.3 Effect of fungicide and cultivar on taro yields plots gave lower yields, low mean tuber weight and fewer tubers. For both cultivars, sprayed plots showed an increase in yield as a respond to increased sprayed frequency. However, yields, number of tubers and mean tuber weight for each cultivar were not significantly different (P< 0.05) in sprayed plots (Table 2). Yields of Ibo coco and mean tuber weight were higher in sprayed plots, compared to Ehkoueh lah. Contrary yields of Ehkoueh lah were higher compared to Ibo coco yields in control plots. Ehkoueh lah produced many tubers both in sprayed and in non-treated plots though with lower mean tuber weight in the later. There was no significant difference in the number of tubers of Ehkoueh lah in sprayed and non-treated plots. Yield increases attributed to fungicide are presented in Table 3. Yield increases were higher with increased spray frequency in both cultivars. Yield increases in Ibo coco were higher than in Ehkoueh lah. Weekly fungicide applications resulted in the highest yield increase of and % in Ibo coco and Ehkoueh lah, respectively. 3.4 Economic analysis of fungicide management Both net return and cost of fungicide protection increased with the number of fungicide applications (Table 4). Total returns were higher for Ehkoueh lah due to it higher market value. Net return was lower for Ehkoueh lah due to high total return obtained from non-treated plots compared to Ibo coco. For both cultivars, net benefit increased with decreased number of fungicide applications, because high costs of fungicide protection were incurred when the number of fungicide application increased. The highest net benefit of 8.27 million FCFAha -1 was obtained in plots sprayed once every month for Ibo coco and 4.81million FCFAha -1 in plots sprayed once every two weeks for Ehkoueh lah. For both cultivars, the least net benefit was obtained when plots were sprayed on weekly bases. The rate of return in both cultivars was highest when plots were sprayed once every month. Ibo coco gave the highest rate of return of Though spray frequency on Ehkoueh lah gave the highest net benefit, the highest rate of return (6.63) was obtained from monthly sprayed plots. 4 Discussions Taro blight was more severe in non-treated plots of each cultivar. This is supported by the high SAUDPC registered by non-treated plots of each cultivar. Among the cultivars Ibo

6 291 Tarla et al coco was more susceptible to taro blight. This can be explained by a high (0.75) SAUDPC in control plots of the Ibo coco cultivar compared to a low (0.63) SAUDPC in control plots of the Ehkoueh lah cultivar. Sprayed plots though received fungicide at different frequencies showed no significant differences amongst themselves for each cultivar. Sprayed plots of each cultivar had their final disease below 25 %. This implies that fungicide reduced the growth rate of taro blight on these plots up to the extent that the severity of the disease could not go above 25% before harvest. Thus it can be concluded that Plantomil 72 WP greatly reduced the severity of taro blight, even when applied at monthly intervals at the rate of 3.33 kg ha -1 kg/ha. Cox Kasimani (1988) and Ghosh and Pan (1991) reported that taro blight was effectively controlled when Ridomil Plus 72 WP was applied at two-week intervals in Papua New Guinea. It was equally reported in 1990 that five applications of Ridomil Plus (3 kg ha -1 ) at three-week interval resulted in an increase of almost 50 % in tuber yields (Cox & Kasimani, 1990). Leaf losses of up to 93 % were recorded in non-treated plots of the Ibo coco. This goes in line with what Gadre & Joshi (2003) reported. Fontem et al.(2001) reported that the same active ingredients, metalaxyl and copper as Ridomil Plus 72 WP significantly reduced late blight (caused by P. infestans (Mont.) de Bary) severity on potato. Yields were significantly different (p < ) between sprayed and non-treated plots for each cultivar. For Ibo coco yields were 16.11t.ha -1 in control plots and between t ha -1 in sprayed plots. There was no significant different between yields in sprayed plots meaning that there was no block effect. The high difference in yields between sprayed and non-treated plots was due to a high taro blight severity in non-treated plots, which greatly reduced the number and surface area of functional leaves, hence, a reduction in photosynthesis. For Ehkoueh lah, the difference between non-treated and sprayed plots was not as high as in Ibo coco. Yields were t ha -1 in non-treated plots and between in sprayed plots. Though taro blight severity was high in non-treated plots of Ehkoueh lah, yields were not greatly reduced. Thus, Ehkoueh lah tolerated the disease as compared to Ibo coco. Number of tubers/ha and mean tuber weight for Ibo coco plots was very much affected, mean tuber weight and number of tubers/ha decreased with increased disease severity. The disease resulted to smaller tubers in non-treated plots which are not very much appreciated by consumers. There was no significant different in the number of tubers/ha in Ehkoueh lah plots. The effect of the disease was shifted to the mean tuber weight. plots gave smaller tubers. Yield increases were high in the Ibo coco cultivar. This improvement were 74.06, 73.69, and 73.35% for,, and fungicide spray schedules, respectively. Yield increases were low in sprayed plots of the Ehkoueh lah cultivar; these increments were 32.5, 31.6, and 29.3% for 1-week, 2-week, 3-week and 4-week fungicide application intervals. This percentage increases falls in the range of yield losses reported by Gadre & Joshi (2003) in many Pacific countries. Guarino (2012) reported taro yield losses of up to 90 % in Cameroon. In some parts of the North West and South West Regions of Cameroon, the disease damaged the farms completely and the farmers have stopped the cultivation of the crop since then. Fontem et al. (1996) reported yield losses of 100 % of tomato fruits due to late blight caused by P. infestans. Later on, Fontem & Schippers (2004) reported a total damage of huckleberry nurseries due to late blight caused by P. infestans. Economic analysis revealed high returns in plots sprayed at weekly intervals, 9.20 and 6.38 million/ha in Ibo coco and Ehkoueh lah plots respectively. Net benefit was rather higher (8.27 million FCFA) in Ibo coco plots sprayed once every month and 4.81 million FCFA in Ehkoueh lah plots sprayed once every two weeks. Based only on net benefit, a monthly spray interval and a 2-week sprayed interval could be adopted for the control of taro blight on the Ibo coco and the Ehkoueh lah cultivar respectively because these spray intervals yielded high revenue. This will however, be wrong; because the rate of return is better placed to say which spray frequency is more economical. Both cultivars showed a high rate of return when plots were sprayed at monthly intervals. Monthly sprayed plots of the Ibo coco and the Ehkoueh lah gave rates of return of and 6.63 million FCFA.ha -1, respectively. This implies that every franc spent in protecting the crop was recovered times for Ibo coco and 6.63 times for Ehkoueh lah. Tarla et al (2011) reported a net return of 2.40 million FCFA.ha -1 and a rate of return of when the same active ingredients were used against huckleberry late blight. Spray regimes with high rates of return are economical and environmentally friendly since less fungicide is discharged to the environment. Conclusions and Recommendations Taro blight is a yield-limiting constraint in taro production in Cameroon; this is supported by high yield increases of up to 74.06%, observed in sprayed plots of Ibo coco. Fungicide applied at the rate of 3.33 kg/ha significantly reduced taro blight severity in both cultivars. Ehkoueh lah cultivar is more tolerant to taro blight compared to the Ibo coco cultivar. Economically, the monthly fungicide spray schedule gave high returns of and 6.63 million FCFA/ha for Ibo coco and Ehkoueh lah cultivars respectively, suggesting the profitability of applying this fungicide against taro blight. Based on the high rate of return recorded by Ibo coco, this cultivar is recommended to growers with month application of Plantomil Plus 72. Taro growers should adopt a spray frequency to limit losses due to blight. Ibo coco cultivar should be cultivated where fungicides are applied while Ehkoueh lah cultivar should be grown without fungicides. Acknowledgement Authors grateful thank Mr Nintai Anthony Ndi of the Faculty of Agronomy and Agricultural Sciences (FASA) for field assistance.

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